When Mays spins the revolver, the single bullet is clearly seen in the next chamber to be fired, and is the one ending up in the firing position after Gabriel cocks the pistol. Once Gabriel fires the gun the first time, and the gun fails to fire, it is obvious that the bullet is either spent already, or the chambers themselves have been re-arranged for dramatic effect.
When Aaron is tied up and gagged, the character played by Robert Patrick takes off his gag. In the next take, the gag is back in place. And then, in the next one, the gag disappear again.
When forced to play the 2 player Russian Roulette the cylinder is spun and then closed. You can see when it is set on the table that the single round is going to be fired next or 2nd to last depending on which way the cylinder spins when cocked. When Gabriel cocks the gun it spins clockwise which puts the round in line with the hammer and firing pin.
Gabriel should have died when he pulled the trigger.
Gabriel should have died when he pulled the trigger.
When Gabriel throws the clock into the field it rings until the credits start (more than forty seconds). Yet he winds up the clock only a little bit which would make it impossible for it to ring that long.
When Mays brings Aaron out of the shed, he takes the rag out of his mouth. In the following shot, after he unties his arm, the rag is back in Aaron's mouth.
The gun that Mays uses to force Gabriel and Aaron to play Russian Roulette with, allows the user to clearly see the chambers, and crucially if the next shot is empty or has the single bullet. An easy way out of the game is for whomever is the next player (Gabriel or Aaron) to look at the chambers, and if they are the unlucky one to get the bullet, quickly point it at Mays and shoot him in the head.